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  • GreatSQL是MySQL的国产分支版本，应用上与MySQL统一。
  • 作者：Yejinrong/叶金荣
  • 文章起源：GreatSQL社区原创
持续吹MySQL 8.0~

在以前，当须要对MySQL数据库进行保护操作时，通常须要先进行主从切换，而后批改设置并重启实例，敞开网络监听，只容许从本地socket形式登入，再进行相应的保护操作；有时候甚至还要批改相应的防火墙，或者罗唆敞开前端业务服务，总体比拟麻烦。

从MySQL 5.7开始，反对设置为离线模式（offline_mode），再有保护操作需要就不必这么麻烦了。只需在线动静批改，可立刻失效，十分的简略粗犷：

mysql> set global offline_mode = on; -- 关上离线模式，回绝内部申请mysql> set global offline_mode = off; -- 敞开离线模式，容许内部连贯申请

当设置为离线模式后，普通用户将无奈持续发动连贯申请，甚至以后正在执行的SQL也会立刻被终止并被断开连接。

1. 无奈创立新连贯

$ mysql -h127.0.0.1 -uyejr -pxx -P4306 sbtestmysql: [Warning] Using a password on the command line interface can be insecure.ERROR 3032 (HY000): The server is currently in offline mode

2. 即使是普通用户通过本地socket连贯，当启用离线模式后，也会被断开

$ mysql -S/data/MySQL/mysql.sock...mysql> show processlist;+-----+------+-----------+------+---------+------+-------+------------------+| Id  | User | Host      | db   | Command | Time | State | Info             |+-----+------+-----------+------+---------+------+-------+------------------+| 304 | yejr | localhost | NULL | Query   |    0 | init  | show processlist |+-----+------+-----------+------+---------+------+-------+------------------+1 row in set (0.00 sec)[sbtest]>select *,sleep(10) from t1 limit 3; -- 正在运行的SQL会立刻被终止，并断开连接ERROR 2013 (HY000): Lost connection to MySQL server during queryNo connection. Trying to reconnect...ERROR 3032 (HY000): The server is currently in offline modeERROR:Can't connect to the server

3. 正在运行中的sysbench压测，也会被立刻断开

[ 1s ] thds: 16 tps: 442.02 qps: 9078.28 (r/w/o: 6382.37/1795.94/899.96) lat (ms,99%,99%,99.9%): 150.29/150.29/150.29 err/s: 0.00 reconn/s: 0.00[ 2s ] thds: 16 tps: 471.23 qps: 9387.56 (r/w/o: 6576.19/1868.91/942.46) lat (ms,99%,99%,99.9%): 61.08/61.08/65.65 err/s: 0.00 reconn/s: 0.00[ 3s ] thds: 16 tps: 386.03 qps: 7712.68 (r/w/o: 5399.48/1541.14/772.07) lat (ms,99%,99%,99.9%): 82.96/82.96/84.47 err/s: 0.00 reconn/s: 0.00[ 4s ] thds: 16 tps: 547.00 qps: 10894.97 (r/w/o: 7609.98/2190.99/1094.00) lat (ms,99%,99%,99.9%): 65.65/65.65/68.05 err/s: 0.00 reconn/s: 0.00FATAL: mysql_drv_query() returned error 2013 (Lost connection to MySQL server during query) for query 'COMMIT'(last message repeated 1 times)FATAL: mysql_drv_query() returned error 2013 (Lost connection to MySQL server during query) for query 'SELECT c FROM sbtest1 WHERE id=4822870'FATAL: mysql_drv_query() returned error 2013 (Lost connection to MySQL server during query) for query 'COMMIT'FATAL: mysql_drv_query() returned error 2013 (Lost connection to MySQL server during query) for query 'UPDATE sbtest1 SET k=k+1 WHERE id=2265001'FATAL: mysql_drv_query() returned error 2013 (Lost connection to MySQL server during query) for query 'SELECT c FROM sbtest8 WHERE id BETWEEN 3389984 AND 3390083'

另外，从MySQL 8.0开始，对于离线模式又做了些改良和欠缺，比方新引入 CONNECTION_ADMIN权限等，细化离线模式的权限管理模式。

简略几点小结对于离线模式：

  1. 必须要有 CONNECTION_ADMIN 以及 CONNECTION_ADMIN权限 或者 SUPER权限（SUPER权限在将来会被废除，而细分成更多细粒度权限），能力在线设置离线模式。
  2. 复制线程不会受到离线模式影响，还能失常工作。
  3. 当设置为离线模式时，没有授予 CONNECTION_ADMIN 或 SUPER 权限的普通用户，正在执行的SQL会被立刻终止，连贯也会被立刻断开。
  4. 当设置为离线模式时，领有 CONNECTION_ADMIN 或 SUPER 权限的用户，不会被断开连接。
  5. 当设置离线模式的用户不具备 SYSTEM_USER 权限（只领有 CONNECTION_ADMIN 以及 CONNECTION_ADMIN权限）的话，领有 SYSTEM_USER 权限的沉闷用户连贯不会被断开（因为想要断开 SYSTEM_USER 权限级别用户连贯同样须要至多有 SYSTEM_USER 权限），详见上面的案例。

有 u1 和 u2 两个用户，受权模式不同

mysql> show grants for u1;+----------------------------------------+| Grants for u1@%                        |+----------------------------------------+| GRANT USAGE ON *.* TO `u1`@`%`         || GRANT SELECT ON `sbtest`.* TO `u1`@`%` |+----------------------------------------+mysql> show grants for u2;+----------------------------------------+| Grants for u2@%                        |+----------------------------------------+| GRANT USAGE ON *.* TO `u2`@`%`         || GRANT SYSTEM_USER ON *.* TO `u2`@`%`   || GRANT SELECT ON `sbtest`.* TO `u2`@`%` |+----------------------------------------+

用户 yejr 的受权模式如下

+--------------------------------------------------------------------+| Grants for yejr@%                                                  |+--------------------------------------------------------------------+| GRANT USAGE ON *.* TO `yejr`@`%`                                   || GRANT CONNECTION_ADMIN,SYSTEM_VARIABLES_ADMIN ON *.* TO `yejr`@`%` || GRANT ALL PRIVILEGES ON `sbtest`.* TO `yejr`@`%`                   |+--------------------------------------------------------------------+

当 yejr 用户设置离线模式后，u2 用户的连贯不会被断开（但不能再建设新连贯），而 u1 用户的连贯会被断开

# 三个用户先别离建设连贯$ jobs[1]   Stopped                 mysql -h127.0.0.1 -uyejr -pxx -P4306 sbtest[2]-  Stopped                 mysql -h127.0.0.1 -uu2 -pxx -P4306 sbtest[3]+  Stopped                 mysql -h127.0.0.1 -uu1 -pxx -P4306 sbtest# 设置离线模式$ fg 1mysql -h127.0.0.1 -uyejr -pxx -P4306 sbtest[yejr@db160] [sbtest]>set global offline_mode=on;Query OK, 0 rows affected (0.00 sec)# u1用户被断开连接$ fg 3mysql -h127.0.0.1 -uu1 -pxx -P4306 sbtest[u1@db160] [sbtest]>select 1;ERROR 2013 (HY000): Lost connection to MySQL server during queryNo connection. Trying to reconnect...ERROR 3032 (HY000): The server is currently in offline modeERROR:Can't connect to the server# u2用户不会被断开连接$ fg 2mysql -h127.0.0.1 -uu2 -pxx -P4306 sbtest[u2@db160] [sbtest]>select 1;+---+| 1 |+---+| 1 |+---+# 但u1/u2用户均不能再建设新链接$ mysql -h127.0.0.1 -uu2 -pxx -P4306 sbtestmysql: [Warning] Using a password on the command line interface can be insecure.ERROR 3032 (HY000): The server is currently in offline mode$ mysql -h127.0.0.1 -uu1 -pxx -P4306 sbtestmysql: [Warning] Using a password on the command line interface can be insecure.ERROR 3032 (HY000): The server is currently in offline mode

是不是有点好玩呀~

联合后面的两篇文章 MySQL 8.0不再放心被垃圾SQL搞爆内存 以及 InnoDB buffer pool size进度更通明 能够看到MySQL 8.0在各个细节方面做的是越来越好了。

延长浏览

  • \#sysvar_offline_mode, https://dev.mysql.com/doc/refman/8.0/en/server-system-variabl...
  • Changes in MySQL 8.0.31, https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-31.html

Enjoy GreatSQL :)

## 对于 GreatSQL

GreatSQL是由万里数据库保护的MySQL分支，专一于晋升MGR可靠性及性能，反对InnoDB并行查问个性，是实用于金融级利用的MySQL分支版本。

相干链接： GreatSQL社区 Gitee GitHub Bilibili

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